Multiplex intermetallic phases in a gravity die-cast Mg−6.0Zn−1.5Nd−0.5Zr (wt%) alloy

Components and crystal structures of the intermetallic phases in a gravity die-cast Mg−6.0Zn−1.5Nd−0.5Zr (wt%) alloy were investigated using transmission electron microscopy. The results indicate that this alloy has multiple intermetallic phases and various inner faults. Totally, six eutectoid intermetallic phases, namely W (MgNdZn3), T (Mg39Zn55Nd6), (Mg,Zr)Zn2, Z (Mg28Zn65Nd7), H2 (Mg15Zn70Nd15), and H1 (Mg24Zn64Nd11), were simultaneously observed at grain boundaries, and six precipitates (Z, Mg7Zn3, T, Mg4Zn7, β1′-MgZn2 and β2′-MgZn2) were found in α-Mg grains. Furthermore, faults like sub-grain boundaries, orientation domains (coherent with the same matching plane but with different orientations), stacking faults and twins were observed in the eutectoid intermetallic phases. Finally, some new orientation relationships between the known intermetallic phases were revealed. This paper can provide new insight into alloy design for Mg−Zn−RE (RE: rare earth) based alloys.